A converter dolly is a coupling device used to connect multiple trailers to a single tractor. The device connects to a hitch on a trailer, and includes at least one axle and a fifth-wheel type connector. The fifth-wheel connector engages the kingpin on an additional trailer to form a tandem or triple-trailer rig, thereby enabling a single tractor to haul an additional trailer with more cargo. Although useful for hauling additional cargo, the converter dolly can be difficult and dangerous to maneuver in reverse. Both the hitch connection and the kingpin connection add pivot points that reduce the amount of control a driver has over the reverse operation of the rig. Careful, close, and time consuming arrangement of the trailers is therefore required to successfully couple multiple trailers together. Devices that prevent rotation of the converter dolly relative to the hitch aide in reverse operation of the tractor-trailer rig and decrease the time required to connect multiple trailers together.
Devices that limit the rotation of a dolly about a hitch face multiple challenges. First, the devices must allow the dolly to normally pivot about the hitch during forward moving left and right turns. Second, a device mounted on a converter dolly must be able to function with multiple makes and models of trailer. Devices that connect only to specific trailer parts are severely limited in their functionality. Third, the devices must be light weight and aerodynamic to reduce the cost of transporting the tandem trailer assemblies. Fourth, the device must be robust enough to withstand road spray from the trailer wheels directly in front of the dolly. Fifth, the device should be easy to operate, and preferably operable from within the tractor cab. Sixth, the device is preferably self-contained so that no parts must be added or removed to operate the device. Seventh, the device must be operable with a dolly that is significantly rotated about a trailer hitch.
Many rotation limiting devices have been proposed. For example, in U.S. Pat. No. 5,348,332 issued to Hamilton and U.S. Pat. No. 2,592,219 issued to West et al., chains attached to the trailer are connected to a dolly to prevent rotation during backwards movement. These designs, however, are not operable from within the tractor cab.
Additionally, the inventions of the '332 and '219 patents require that the trailers have specific loops or features to which the chains are connected. Finally, the chains of the '332 and '219 must be manually removed when not in use.
In U.S. Pat. No. 3,421,777 issued to Barker et al., mechanical plungers are manually ratcheted forward from a dolly. The plungers extend to laterally spaced bumpers (22 in FIG. 3 of the '777 patent). Although the mechanism is self contained, the lateral spacing of the bumpers is not standard among trailers and therefore the device would not be operable with many trailer makes and models. The device of the '777 patent is also not functional with a converter dolly that is significantly rotated since the plungers 23 shown in FIG. 3 would pass to the sides of the bumpers 22 (numbers and figures refer to the '777 patent).
In U.S. Pat. No. 4,603,876 issued to Gray and U.S. Pat. No. 3,815,939 issued to Pettay, swinging arms extend from the dolly to multiple contact locations, thus preventing the converter from pivoting substantially when the arms are engaged. These designs, however, require that the trailer has specific features for receiving the swing arms (109 in FIG. 2 of the '876 patent) and that the receiving features be at the same elevation as the converter dolly. The receiving features and elevation requirements limit the utility of the inventions of the '876 and '939 patents to specific makes and models of trailers. As with the other references, the inventions of these patents are not operable with significantly rotated dollies.
Accordingly, an object of the present invention is to provide a device capable of restricting rotation of a converter dolly about a trailer hitch, thus simplifying and expediting trailer coupling.
A further object of the present invention is to provide a device mounted on a converter dolly that is light weight, aerodynamic, and robust.
Another object of the invention is to provide a converter dolly backup device that is functional with many trailer makes and models.
Yet another object of the present invention is to provide a device operable from within a tractor cab, preferably utilizing the standard electrical or air systems on a trailer.
Another object of the present invention is to provide a device that is self contained without components that must be removed or added to operate the device.
Finally, an object of the present invention is to provide a device that is operable with a trailer and dolly that are significantly rotated with respect to each other.